In the past, various types of metal detectors, magnets, microswitches and eddy current devices have been utilized to protect the carding machine from damage due to foreign objects being present in the lap being fed into the card. All of these devices have fallen far short of desired goals, and the use of some of the devices installed at or under the feed roll of the card have resulted in more costly damage than they prevent. Other devices will only detect metal and will not detect nonferrous metals or other hard materials capable of damaging the card. Such materials include glass, rock, wood, plastics, leather and the like. Damage from such foreign objects can necessitate costly repairs or rebuilding of the card, as is well known.
The object of this invention, therefore, is to provide a foreign object detector which can detect minute objects having a thickness of as little as 0.001 inch with a lateral dimension of about 3/32 inch, regardless of the material the hard object is made of. Furthermore, the mechanical detector can act twice or more on every advancing region of the lap before the lap enters the feed roll. Individual foreign object feeler pins compactly arranged in staggered relationship in multiple rows assure that no foreign objects in the lap will escape detection. When such an object, or objects are detected by the mechanism, the doffer and feed roll will be stopped automatically and cannot be restarted by the operator until the foreign object is removed from the lap, thus assuring complete protection of the card. An indicator is included in the device to alert the operator to the presence of foreign objects and a convenient viewing panel is provided through which the operator can directly observe which feeler pin have been elevated by contact with a foreign object.
The operational capability of the invention in protecting the card is far in excess of any known prior art system.
Other features and advantages of the invention will become apparent during the course of the following detailed description.